Abstract
Sealing can arrest caries lesions. We aimed to evaluate if sealing effects and kinetics are bacterial-strain and sealing-material specific. Human dentin discs were mounted in a dual-chamber device. Caries lesions were induced chemically and contaminated with either Lactobacillus rhamnosus (LR) or Streptococcus sobrinus (SS). For (1) kinetics assessment, the initial bacterial load and the sealing period were varied, and lesions sealed using a self-etch adhesive and composite. For (2) comparing materials, six sealing protocols (#1-#6) were evaluated: 1# Self-etch adhesive plus composite placed without a liner, or #2 calcium hydroxide, or #3 mineral trioxide aggregate, or #4 Biodentine liners; #5 antibacterial adhesive plus composite; #6 glass ionomer cement. Pulpal fluid flow was simulated during sealing. The outcome was the number of surviving bacteria (CFU) per g dentin. For LR, bacterial survival increased significantly with increasing initial bacterial load and decreased with longer sealing periods. The relative reduction followed a first-order kinetics. More LR survived under calcium hydroxide or MTA than other materials (p < 0.001). For SS, nearly no bacteria survived sealing regardless of sealing period, initial bacterial load or sealing material. In conclusion, sealing effects and kinetics were strain- and material-specific.
Highlights
IntroductionThe traditional non-selective (‘complete’) carious tissue removal is not recommended any longer[1]
For deep carious lesions, the traditional non-selective (‘complete’) carious tissue removal is not recommended any longer[1]
The remaining number of Lactobacillus rhamnosus (LR) after sealing was found to be significantly affected by the initial bacterial load (β = 0.53 [95% CI: 0.43/0.62] × 106 CFU/g, p < 0.001) i.e. the remaining number of LR increased by 0.53 × 106 CFU/g per 106 CFU/g being present initially
Summary
The traditional non-selective (‘complete’) carious tissue removal is not recommended any longer[1]. Survival of sealed bacteria might depend on the number of sealed bacteria, with large numbers of bacteria (as a result of leaving soft or very soft instead of leathery or firm dentin, for example) being more difficult to inactivate In this case, providing antibacterial cavity treatments or using antibacterial restorative strategies could be relevant. Such system should incorporate the simulation of pulpal fluid flow, as this might be decisive for any sealing effects in a clinical setting Using such preclinical testing system would allow to standardize carious lesions (with regards to bacterial numbers and strains), the residual dentin thickness, and the pulpal fluid composition and pressure. We compared the effects of different restorative strategies on sealed bacteria, hypothesizing that different materials would yield significantly different numbers of surviving sealed bacteria
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